Add missing emoji_events field support for Project Webhooks

Add emoji_events support for Project Webhooks

Description

I'm trying to configure a project webhook to receive emoji reaction events, but the Go SDK doesn't support the emoji_events parameter for project webhooks.

According to the GitLab API documentation, project webhooks support emoji_events since GitLab 16.0, but I cannot enable this feature when creating or updating webhooks through the Go SDK.

Expected Behavior

I should be able to:

• Enable emoji_events when creating a new project webhook
• Update an existing project webhook to enable/disable emoji_events
• Read the emoji_events status when retrieving webhook information

Current Behavior

The SDK does not provide any way to configure emoji_events for project webhooks. This forces me to manually configure webhooks through the GitLab UI instead of automating the setup.

Additional Context

• Group webhooks already support emoji_events in the SDK
• The GitLab API supports this for both project and group webhooks
• This feature is documented in the official API docs since GitLab 16.0

References

• GitLab Project Webhooks API
• GitLab Trigger Test Webhook

Implementation Guide

• Read the CONTRIBUTING.md guide for setting up your local development environment and clone the community fork of this project.
• In projects.go, add a new bool field called EmojiEvents to the ProjectHook, AddProjectHookOptions and EditProjectHookOptions structs.
• In projects_test.go, ensure there is test coverage for the new field in the get, create and update project hook tests.
• Run make reviewable and raise an MR with your changes.